The present invention relates to the technical field of household electric cooking appliances of the toaster type and concerns more particularly an appliance whose heating elements are constituted by transparent walls.
U.S. Pat. No. 2,564,677 discloses a toaster whose heating elements are transparent walls, such as glass plates, covered with a metal oxide layer having a base of tin and indium oxide, subsequently commonly called ITO (for xe2x80x9cIndium Tin Oxidexe2x80x9d). This layer, whose thickness is between 0.3 xcexcm and 0.7 xcexcm, is transparent and resistive, so that when connected to an electric power supply, it is heated to a temperature needed to toast a bread slice or slices placed between the walls. Such elements can thus be utilized in order to control the toasting process while allowing direct observation of the degree of browning of the bread.
Devices permitting the reheating of rolls and similar food items are also known, this reheating function being performed with the aid of an additional removable accessory, which comes to be positioned above the opening of the toasting chamber as described in the patent document DE G 9115161.9, or with the aid of an accessory that is integrated into the toaster, but can be moved out of the way when it is not needed.
Patent document DE G 9316913.2 describes a toaster having a reheating means composed of two rigid metal wires that can open out in rotation around an axis in a manner to form a support disposed at a distance above the toaster.
Although such a system offers acceptable results, the mechanism for rotating the wires can deteriorate or sag under the weight of the food to be reheated. In addition, such a device requires additional parts, notably for rotation of the wires, which increases the price at which the toaster can be sold.
Moreover, this device is not compatible with, or adaptable to, a form of construction that allows viewing the bread that is being subjected to the action of the heating elements.
An object of the present invention is to overcome the problems presented by the prior art, without providing a removable accessory for reheating rolls, which accessory is often difficult to put away and can be lost, while assuring the most complete observation possible of the bread that is being toasted or reheated.
The present invention provides a toaster having a base and at least two substantially vertical heating elements defining a cooking, or toasting, space that is open at least at the upper part of the toaster. The heating elements are in the form of transparent glass walls each composed of a glass substrate covered, on one of its faces, with a resistive layer of metal oxide or oxide. The metal oxide layer is connected to an electric supply circuit that supplies heating current and at least two of the glass walls each have an upper rim, or lip, made of a transparent material.
Such a rim or lip is intended to be a part of the upper edge of the wall or of a piece connected at this level which projects laterally to form a border portion. With this configuration, the reheating of rolls and pastries is correctly assured, while permitting a visual observation thereof, in order to avoid particularly an undue browning while the rims remain in esthetic harmony with the transparent glass walls. Moreover, this principle avoids the need for a removable device that is difficult to store and capable of being lost. In addition, the transparent appearance of the rim avoids the cluttered appearance associated with such a function with an accessory that is partially metallic and is mounted permanently on the toaster.
According to one specific form of construction of the invention, the rims are oriented toward the exterior of the toasting space, thus presenting a sufficiently large bread receiving plate or dish, assuring the stability of the bread or other food product as it rests on the rims.
Advantageously, the rims of the glass walls have bosses that present support points at different heights and assuring a passage of hot air between the rims and the food product resting thereon. The product is thus heated in a more homogeneous manner.
According to another form of construction of the invention, the rims of the glass walls are inclined to slope downwardly toward the opening of the toasting space. This slope assures an automatic centering and better stability for the products placed on the rims.
According to another form of construction of the invention, the rim of each glass wall has, on the face opposed to that receiving the food product, an electric resistance member arranged to be heated when it is connected to a current source.
This arrangement permits the lateral faces of the products to be heated locally, bringing a complementary heating to that generated in the toasting space by the heating walls. The complementary heating elements on the rims speed up reheating of products that rest on the rims.
Advantageously, the resistance member on each rim element is a layer of metal oxide or oxides assuring transparency in harmony with the main heating elements.
According to the invention, transparent covers are disposed close to the faces of the glass walls that are covered with the layers of metal oxide or oxides. These transparent covers protect the electrically active surfaces by preventing them from being contacted by users. Their transparency allows viewing of the bread that is being toasted or the product that is being reheated.
Advantageously, each substrate and its rims are made in one piece of pressed glass, fabricated in a molding operation.
This fabrication process permits, in a single molding operation, the formation of the flat substrate and of the rim, without incurring additional costs to provide for the reheating function while achieving a continuity of the wall and its rim, without requiring any separate attachment operation, such as welding, soldering or bonding between each main wall and its associated rim.